1. Field of the Invention
The present invention relates to a plasma processing apparatus for applying plasma processing to an article to be processed (hereinafter, simply referred to as xe2x80x9carticlexe2x80x9d as occasion demands) using microwaves, and more particularly to a microwave applicator having an annular (or circular) waveguide, a plasma processing apparatus provided therewith, a microwave applicator having a multiple annular waveguide, and a plasma processing apparatus provided therewith.
2. Related Background Art
As plasma processing apparatuses that use microwaves as an excitation source for plasma generation, there have been known the plasma polymerizing apparatus, the CVD apparatus, the surface modifying apparatus, the etching apparatus, the ashing apparatus, and the cleaning apparatus and the like.
The CVD using such a so-called microwave plasma processing apparatus is carried out, for example, as follows. A gas is introduced into a plasma generation chamber and/or a film formation chamber of a microwave plasma CVD apparatus, and a microwave energy is simultaneously applied to generate a plasma in the plasma generation chamber to excite and/or decompose the gas, thereby forming a deposited film on an article to be processed disposed in the plasma generation chamber or film formation chamber. Further, a similar method can be used to carry out plasma polymerization of an organic substance or surface modification such as oxidation, nitridation or fluorination.
Furthermore, the etching using a microwave plasma etching apparatus is carried out, for example, as follows. An etchant gas is introduced into a processing chamber of the apparatus, and a microwave energy is simultaneously applied to excite and/or decompose the etchant gas to generate a plasma in the processing chamber, thereby etching the surface of an article to be processed disposed in the processing chamber.
In addition, the ashing using a microwave plasma ashing apparatus is carried out, for example, as follows. An ashing gas is introduced into a processing chamber in the apparatus, and a microwave energy is simultaneously applied to excite and/or decompose the ashing gas in order to generate a plasma in the processing chamber, thereby ashing the surface of an article to be processed, namely a photoresist disposed in the processing chamber. As with the ashing, it is possible to effect cleaning for removing unwanted matter deposited on a to-be-processed surface of an article to be processed.
In the microwave plasma processing apparatus, since microwaves are used as a gas excitation source, electrons can be accelerated by an electric field having a high frequency, thereby efficiently ionizing and excite gas molecules. Thus, the microwave plasma processing apparatus is advantageous in that the efficiency of ionization, excitation, and decomposition of a gas is high, so that a high density plasma can relatively easily be formed, thereby enabling fast processing at a low temperature to provide high quality. In addition, since the microwaves have a property of penetrating a dielectric member, the plasma processing apparatus can be constituted as a electrodeless discharge type, whereby highly clean plasma processing can be carried out.
To increase the processing speed of the microwave plasma processing apparatus, plasma processing apparatuses using electron cyclotron resonance (ECR) have been put to practical use. The ECR is a phenomenon in which when the magnetic flux density is 87.5 mT, the electron cyclotron frequency for electrons rotating around the magnetic line of force is brought into conformity with the general frequency of the microwaves of 2.45 GHz, whereby the electrons resonantly absorb microwaves to be accelerated, thereby generating a high density plasma. As to such an ECR plasma processing apparatus, the following four typical configurations for a microwave introducing means and a magnetic-field generating means are known.
In a first configuration (i), microwaves propagated via a waveguide are introduced into a cylindrical plasma generation chamber from a surface opposed to an article to be processed through a transmissive window, and a divergent magnetic field coaxial with the central axis of the plasma generation chamber is introduced via an electromagnetic coil provided at the periphery of the plasma generation chamber. In a second configuration (ii), microwaves transmitted via a waveguide are introduced into a bell-shaped plasma generation chamber from a surface opposed to an article to be processed, and a magnetic field coaxial with the central axis of the plasma generation chamber is introduced via an electromagnetic coil provided at the periphery of the plasma generation chamber. In a third configuration (iii), microwaves are introduced into a plasma generation chamber from its periphery via a coil that is a kind of a cylindrical slot antenna, and a magnetic field coaxial with the central axis of the plasma generation chamber is introduced via an electromagnetic coil provided at the periphery of the plasma generation chamber. In a fourth configuration (iv), microwaves transmitted via a waveguide are introduced into a cylindrical plasma generation chamber from a surface opposed to an article to be processed via a planar slot antenna, and a loop-like magnetic field parallel to the antenna plane is introduced via a permanent magnet provided on the rear surface of the planar antenna (planar slot antenna method).
Further, U.S. Pat. No. 5,034,086 discloses a plasma processing apparatus using a radial line slot antenna (RLSA).
In addition, Japanese Patent Application Laid-Open No. 5-290995, U.S. Pat. No. 5,359,177, and EP 0564359 disclose a plasma processing apparatus using an annular waveguide with terminals.
Separately, as an example of a microwave plasma processing apparatus, there has recently been proposed an apparatus using an annular waveguide in which a plurality of slots are formed on an inner side surface thereof as a device for uniform and efficient introduction of microwaves (Japanese Patent Application Laid-Open No. 5-345982; U.S. Pat. No. 5,538,699).
This microwave plasma processing apparatus is shown in FIG. 29 and a microwave supply means thereof is shown in FIG. 28.
Reference numeral 501 designates a plasma generation chamber; 502 is a dielectric window that separates the plasma generation chamber 501 from the atmosphere; 503 is a slotted endless annular waveguide with a cylindrical external shape for supplying microwaves to the plasma generation chamber 501; 505 is a plasma-generating gas supply means; 511 is a processing chamber connected to the plasma generation chamber 501; 512 is an article to be processed; 513 is a support for the article 512; 514 is a heater for heating the article 512; 515 is a processing gas supply means; 516 is an exhaust port; 521 is a block that distributes microwaves to the right and left; and 522 is a slot provided in a curved surface 523. In addition, 524 is a diaphragm and 525 is a microwave introducing port.
The generation of a plasma and the processing are carried out as follows.
The inside of the plasma generation chamber 501 and the processing chamber 511 is evacuated via an exhaust system (not shown). Subsequently, a plasma generating gas is introduced into the plasma generation chamber 501 at a predetermined flow rate via the gas supply port 505.
Then, a conductance valve (not shown) provided in the exhaust system (not shown) is adjusted to retain the inside of the plasma generation chamber 501 at a predetermined pressure. A desired power is supplied to the inside of the plasma generation chamber 501 from a microwave power source (not shown) via the annular waveguide 503.
On this occasion, the microwaves introduced into the annular waveguide 503 are distributed to the right and left by the distributing block 521 and propagate through the waveguide at a guide wavelength longer than a free-space wavelength. The microwaves are supplied from the slots 522 provided at an interval of xc2xd or xc2xc of the guide wavelength, through the dielectric window 502 to the plasma generation chamber 501 to generate a plasma 527.
At this time, when a processing gas has been supplied into the processing chamber 511 via the processing gas supply pipe 515, the processing gas is excited by the high density plasma as generated to process a surface of the article to be processed 512 put on the support 513.
Since the use of such a microwave plasma processing apparatus can generate a high density, low potential plasma of a uniformity within xc2x13%, an electron density 1012/cm3 or more, an electron temperature 3 eV or less, and a plasma potential 20V or less in a space of a diameter of about 200 mm at a microwave power of xe2x88x921 kW or more, the gas can fully be reacted and supplied in an active state to the article to be processed and the surface damage due to incident ions of the article to be processed can be reduced, thereby enabling high quality and high speed processing even at low temperatures.
However, when the microwave plasma processing apparatus that generates a high density, low potential plasma as shown in FIGS. 28 and 29 is used to effect processing in a high pressure region at 100 mTorr (about 13.3322 Pa) or more, as in the case of the ashing processing, the diffusion of plasma is suppressed, so that the plasma may locally exist in the periphery of the chamber to reduce the processing speed for the center portion of the article to be processed.
Further, Japanese Patent Application Laid-Open No. 7-90591 discloses a plasma processing apparatus using a disc-like microwave introducing device. In this apparatus, a gas is introduced into a waveguide and emitted toward a plasma generation chamber through slots provided in the waveguide. In this apparatus, in order to prevent a plasma from being generated in the waveguide, the gas supply pressure, the conductance in the waveguide, the conductance of the slots, the exhaust pressure, and the like must be adjusted precisely. It is thus very difficult to design an apparatus that can be commonly used for any one of the CVD, etching, ashing, and so on the optimal pressures for which are different from one another.
In addition, for the processing of the surfaces of a 12-inch wafer (also called xe2x80x9c300 mm waferxe2x80x9d) of a diameter 305 mm, a glass substrate of an area equivalent thereto, and the like as required in recent years, a layer of a high density plasma is needed which is uniform, of a large area, and thin.
To provide such a plasma layer, the configuration of a gas supply means and/or the configuration of a microwave supply means need to be further improved.
A first object of the present invention is to provide a plasma processing apparatus and method that can perform various higher-quality plasma processing of higher quality at lower temperatures.
A second object of the present invention is to improve a gas supply means and to therefore provide a plasma processing apparatus and method that can generate a layer of a high density plasma which is uniform, of a large area, and thin, even when the processing is carried out in a region of a relatively high pressure.
A third object of the present invention is to provide a microwave applicator of a simple and inexpensive structure that can provide various microwave radiant intensity distributions.
A fourth object of the present invention is to improve a microwave supply means and to therefore provide a microwave applicator and a plasma processing apparatus and method that can generate a layer of a high density plasma which is uniform, of a large area, and thin.
A fifth object of the present invention is to provide a microwave applicator and a plasma processing apparatus and method that can plasma-process a large area article to be processed equivalent to a wafer of a diameter of 300 mm or more.
The gist of the present invention resides in a microwave applicator having a slot provided in the plane of an annular waveguide and a plasma processing apparatus and method using the same.
According to a first aspect of the present invention, there is provided a plasma processing apparatus comprising a container which can be evacuated; a gas supply means for supplying a gas to the inside of the container; and a microwave supply means for supplying microwaves to generate a plasma in the container, the plasma being utilized to process an article, wherein the microwave supply means is a microwave applicator which is provided with an annular waveguide having a planar H-plane with a plurality of slots provided apart from each other and a rectangular cross section perpendicular to the traveling direction of microwaves and which supplies microwaves to the inside of the container through a dielectric window of the container from the plurality of slots provided in the planar H-plane, and wherein the gas supply means is provided a gas emission port through which the gas is emitted toward the planar H-plane.
This configuration can generate a uniform, large-area, and low-temperature plasma even at a relatively high pressure, whereby a large-area article to be processed equivalent to a 8-inch or more wafer can be processed.
According to a second aspect of the present invention, there is provided a microwave applicator which is provided with an annular waveguide having a plane with a plurality of slots provided apart from each other and a rectangular cross section perpendicular to the traveling direction of microwaves and which supplies microwaves to the outside of the annular waveguide from the plurality of slots provided in the plane, wherein an assembly comprising a conductive member having an annular recessed portion and a microwave introducing port formed therein and a plate-like conductive member having the plurality of slots formed therein forms the annular waveguide in which the plane with the plurality of slots forms an H-plane.
This configuration enables a low-cost and highly universal microwave applicator to be manufactured.
According to a third aspect of the present invention, there is provided a plasma processing apparatus comprising a container which can be evacuated; a gas supply means for supplying a gas to the inside of the container; and a microwave supply means for supplying microwaves to generate a plasma in the container, the plasma being utilized to process an article, wherein the microwave supply means is a microwave applicator which is provided concentrically with a plurality of annular waveguides each having a planar H-plane with a plurality of slots provided apart from each other and a rectangular cross section perpendicular to the traveling direction of microwaves and which supplies microwaves to the inside of the container through a dielectric window of the container from the plurality of slots provided in the planar H-plane of each of the plurality of annular waveguides.
This configuration can generate a uniform, large-area, and low-temperature plasma regardless of flow of the gas, whereby a large-area article to be processed equivalent to a 12-inch or more wafer can be processed.